I. Field of the Invention
The present invention relates to radio frequency (RF) test circuits for dual-band transceivers. More particularly, the present invention relates to a novel and improved dual-band RF test circuit for interfacing with a dual-band wireless communication device.
II. Description of the Related Art
In the field of RF testing, test equipment is generally connected to a unit under test via a test interface. The purpose of the test interface is to provide a proper impedance match, signal level, and connection of the unit under test to the test equipment. For example, a wireless transceiver such as a cellular or PCS-band telephone may be connected to RF test equipment during manufacture testing or repair in order to determine the "health" of the circuitry inside the wireless transceiver, and diagnose problems.
In the past, specialized test equipment interface circuits have been designed which are custom-tailored to the unit under test. For example, if the unit under test is a portable cellular telephone, then the test equipment interface circuit would be optimized to provide a proper match of the unit under test to the test equipment at cellular frequencies (i.e., frequencies in the 800 MHz range). On the other hand, if the unit under test is a portable PCS-band telephone, then the test equipment interface circuit would be optimized to provide a proper match of the unit under test to the test equipment at PCS-band frequencies (i.e., frequencies in the 1900 MHz range).
In a high-volume manufacturing and testing environment, where there may be a few different models of wireless transceivers being tested, each operating on a different radio frequency band, it is inefficient and costly to have separate RF test stations for each model of wireless transceiver when the only significant difference between their RF performance is that they are operating in different frequency bands. Thus, there is a need felt in the art to be able to test various models of wireless transceivers at the same test station, particularly if one of the models is a dual-band transceiver which itself is capable of operating on more than one frequency.
However, if multiple frequencies are to be tested at the same test station, the multiple types of test interfaces would also be needed; each optimized for its respective frequency band. It becomes time consuming, and thus costly to manually switch between these test interfaces in a high-volume testing environment.
One way to solve the problem of multiple test equipment interfaces is to use an active (i.e., powered) switch, or a mechanical switch, to switch between the various required interfaces. However, using active switches increases the complexity of the test setup because it requires power to be routed to the test equipment interface circuit. Thus, it would be advantageous to provide a test equipment interface circuit that does not require external power. Mechanical switches are also undesirable in a high-volume manufacturing environment because they tend to wear out very quickly. Moreover, they require that the operator of the test setup remember to operate the switch to change between the various test equipment interface circuits. Thus, it would be advantageous to provide a test equipment interface circuit that does not require a mechanical switch. In sum, what is needed is a test equipment interface circuit that is capable of operating on more than one frequency, but is easy to operate and efficient.